Hair is subjected to thermal damage during hair drying, e.g., by repetitive blow dryer actions, and also during the use of an iron for curling or straightening hair. Such heat damage is enhanced in the presence of moisture and tensile stresses to cause buckling of the hair cuticles. Cuticle lifting makes the hair duller and feel less smooth.
Virgin hair surface is hydrophobic and is less prone to heat damage than bleached hair, which is usually hydrophilic. Restoration of hair hydrophobicity, which endures many wash cycles is also desirable to help protect the hair upon application of heat in the presence of moisture.
Permanent or semi permanent hair straightening and hair curling has become extremely popular. Chemicals that provide permanent hair straightening have been known for a long time: hydroxides, reducing agents such as thiols and sulfites. However, due to their strong alkalinity, these treatments tend to be harsh for the scalp and the hair.
Alternatively, effective treatments although non alkaline were often found sensitizing to the skin. Many recent developments have been aimed at finding treatments which are effective, but cause less of the aforementioned issues.
The use of oils and silicones in hair treatments has been known for a long time. Nevertheless, there still exists a need for silicones that can facilitate hair straightening or shaping processes involving the use of heat while also providing improved thermal protection.